JPS62251071A - Device for grinding or polishing workpiece - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A workpiece is pressed against a grinding or polishing disc under the action of an actuating force transmitted to this workpiece, thus:
The present invention relates to an apparatus for grinding or polishing a workpiece, in particular a metallographic sample, which is subjected to an actuation force, i.e. a grinding or polishing pressure equal to the actuation force divided by the surface area of the workpiece being ground or polished.

When such equipment is used for grinding (including sharpening) or polishing, wear occurs. That is, material is removed from the surface of the sample that is in contact with the grinding or polishing disc.

Particularly in the field of metallography, it is customary to remove a surface layer of a predetermined thickness, in other words to obtain a predetermined wear depth, ie to obtain a predetermined wear depth of a predetermined magnitude at a certain speed.

To achieve this, hitherto it has been common practice to use process time as a parameter. This means that grinding or polishing is finished after a predetermined process time established empirically. However, this method involves considerable uncertainties, so that, for example, if the wear characteristics of the grinding wheel change, the wear depth per unit time will therefore differ from the value on which the working time was determined.

It is therefore preferable to be able to carry out direct measurements of wear depth. Such measurements are obtained by optical measuring systems similar to those used in modern machine tools for measuring distances in the μm range. Although such systems are highly accurate, they are too expensive to be used in conjunction with conventional metallographic grinding and polishing and do not indicate grinding or polishing pressure. This pressure, which is also an important parameter of the process, must therefore be measured separately.

It is an object of the invention to provide a device of the above type, which allows the grinding or polishing pressure and the wear depth to be measured together at low cost for a measuring device.

To achieve this, a feature of the invention is that an elastically deformable transmission link is provided in the power transmission path for the actuating force, and at the end of the power transmission path opposite the workpiece. An actuating member is provided which distorts the elastically deformable link at the beginning of grinding or polishing and maintains this strained condition until a desired value of actuating force or pressure is obtained and then during the course of the process. is kept stationary and the device detects the elastic deformation of the transmission link and its deformation changes that occur during the process and measures both the actuating force, i.e. the pressure, and the wear depth from the values established by the detection. The apparatus further includes means.

In the device according to the invention, the actuating force is transmitted from a point in the locked position via an elastically deformable transmission link, so that the actuating force gradually decreases during grinding as wear progresses. The difference between the value of the actuating force or pressure at a given time and the value of the actuating force or pressure at the start of grinding or polishing is therefore a measure of the depth of wear. The instantaneous value of the elastic deformation of the transmission link therefore provides a measure of both the actuation force and the wear depth at any stage of the process. As is known, the elastic deformation of an object can be measured by simple and inexpensive transducers, such as strain gauges or capacitive transducers, and simple electronic equipment that processes the measurement results and makes them available for display and/or process control.

The electronic device can include a microprocessor into which parameters can be written to control the process according to a desired program.

For example, if at a given point in the process it is desired to reduce the actuating force or pressure beyond the automatically occurring reduction value, the desired reduction in actuating force or pressure is achieved and the wear depth measured just before the reset is A program can be installed in the microcomputer to store the value and reset the actuating member to count the wear depth from the memorized value according to the decreasing value of the actuating value after resetting.

Another possibility, which is often advantageous, is to read the desired wear depth as a control parameter of the process so that the process is terminated when the desired wear depth is reached. When using a grinding wheel in this connection, the grinding wheel is long enough to achieve the desired depth of wear within a predetermined maximum time after the initial sharpening;
Wear characteristics may not be maintained. In this case, the electronic automation system can be programmed to interrupt grinding to begin sharpening, and then continue grinding.

Even in this case, the wear depth value is memorized during the temporary interruption and continues counting from the point at which the process continues.

The device can be provided in a known manner with a rotating sample holder, by means of which the workpiece is moved internally during the process about an axis eccentric to the axis of the grinding or polishing disc. .

Since it is known that mechanical devices cannot be manufactured without certain tolerances and that neither the sample holder nor the grinding/polishing disk can rotate without certain asymmetries, it is necessary to determine an average point from which to calculate the wear depth. The measured values can be improved. As the process progresses, similar averaging calculations are made to calculate the wear depth.

Depending on the polishing element (grinding/polishing disc) used, this average calculation can be performed over one or multiple revolutions of the sample holder.

The duration of the averaging calculation can be determined purely electronically or by means of angle-indicating signals from rotating parts.

The invention will now be described in more detail with reference to the accompanying drawings.

A metallographic sample 2 is placed on a grinding/polishing disk 1 which is rotatably mounted in the frame of the apparatus, and a force P transmitted from a rotating shaft 16 is applied to a pressing shoe 3 as shown in FIG. engage.

The sample is guided by a drive plate 15, which has at least one hole for supporting the sample, and which is fixed via four stays 21 to the sample holder head 4, which rotates together with a shaft 16. is connected to.

The rotation is carried out by an electric motor 5.

The shaft 16 can also move vertically, and this movement
Place the sample 2 on the drive plate 15 and apply the necessary force P.
It must be done in a way that conveys the message. This vertical movement is performed by the gear motor 2, and the gear motor 2
operates the rack 14 via the pinion 13. This gear motor 2 is fixedly attached to the frame of the device.

When it is desired to move the sample holder head downward, the gear motor 2 is started and the rack 14 is moved downward. This movement is transmitted to the bar 11 via the pivot connection. This bar 11 is connected to a pivot bar 8 via an elastic bar 9. Two strain gauges (half bridges) 10 are attached to the bar 9. This bar 8 acts on the shaft via the bracket 17 so that the shaft 1 presses the sample 2 onto the grinding or polishing disc 1.
6 is pressed downward by the bracket 17, the elastic bar 9 is elastically bent, and the amount of bending is determined by the strain gauge 10.
Detected by

The gear motor 2 is self-locking so that when it stops, the rack 14 is stuck in the moved position.

The rotational movement of the shaft 16 and thus of the sample holder head 4 can be read by the inductive sensor 7 and the rotating toothed disc 6 .

The gear motor 12, the strain gauge 10, and the sensor 7 are connected to an electronic control device, which includes a comparator 22 with a Schmitt trigger, a differential amplifier 23, an analog/digital converter 24, a microprocessor 25, It consists of a pressure control unit 26 and a display 27 for displaying pressure and wear depth.

At the beginning of the polishing process, the surface of the sample is indicated at 18, and as the process progresses, material is removed, as indicated by the hatched areas 9, and a new surface 20 is formed at the end of the process.

If it is desired to remove a predetermined number of μm, as indicated by the reference numeral 19, this is done as follows (compare with FIG. 1).

Drive plate 15 connected to sample holder head 4
The sample 2 is then moved by a gear motor 12 towards a rotating grinding or polishing disk 1 .

Once the desired pressure is achieved, the current to the gear motor 12 is cut off, so that the lower arm 11 does not move. Thereafter, the microprocessor waits for a signal from the inductive position sensor 7. When the signal arrives, the A/D converter is started and the voltage from the strain gauge differential amplifier indicating the vertical position of sample 2 is read by the microprocessor. While the sample holder head 4 continues to rotate, new values are read and the average value is calculated once the sample holder head has rotated through the exact rotation angle of 360° read by the position sensor 7. This value now indicates the initial vertical position of the sample. One average calculation is followed by another, and the grinding/polishing operation is stopped when the gap between the last average calculation value and the average calculation value representing the initial position is equal to a certain wear depth. be done.

The reason why measured values must be used only after averaging over 360° is due to mechanical tolerances.
This is because the vertical position of the sample changes depending on the horizontal position.

Furthermore, the measurement method varies depending on whether a grinding wheel or an abrasive disc is used. When using a grinding wheel, it is sufficient to average over 360° since the grinding wheel is sharpened in the same device so that the vertical position of the sample is independent of the rotation of the grinding wheel. For abrasive discs,
Since there is no abrasion, the position of the sample is determined not only by the rotation of the sample-holding head, but also by the rotation of the polishing disk. Therefore, the averaging calculation must be performed over a large number of revolutions of the sample holding head so that the contribution from the polishing disk itself is included in the averaging function.

As is clear from the above explanation, there is a consistency between the polishing rate and the average time, so for grinding discs that wear quickly, the initial position calculation must be completed quickly. , it can be seen that in the case of an abrasive disk with a slow wear rate, a somewhat longer time is acceptable.

Some numerical examples are given below to further illustrate the method.

The pressure per sample can vary from 50-6 ON for grinding or polishing to 3N for precision polishing.

During the process, when par 11 is stopped, the pressure gradually decreases as material is removed from sample 19. Although this pressure drop is not large, it has an advantageous effect, since in principle it is often preferred to reduce the pressure towards the end of the process.

The pressure drop is determined by the elastic modulus of the elastic bar 9. In a typical example, the pressure drop reaches 3N per 0.1 n downward movement of sample 2. As a result, 0.2H
For a depth of material removal reaching 19, there will be a 12% pressure drop with a final pressure of 5ON.

The amount of material removed from the sample is typically between 0.1 and 9.
5. That's a lot of vans. The wear depth is measured within a tolerance of ±5 μm to 110 μm depending on the mechanical and electronic structure of the device.

[Brief explanation of drawings]

1 is a schematic representation of an embodiment of the device according to the invention, with the mechanical parts seen from the side and partly in diametrical section; FIG. 2 is an enlarged detailed view of a part of the device; FIG. It is. 1... Grinding or polishing disk, 2... Workpiece, 8.9.11... Elastically deformable link, 10.
...detection means, 14...actuation member, 4.15...sample holder, 25...microprocessor.

Claims (3)

[Claims] (1) The workpiece 2 is pressed against the grinding or polishing disc 1 under the action of an actuating force transmitted to the workpiece and is thus subjected to a grinding or polishing pressure. A device for polishing, in which elastically deformable transmission links 8, 9, 11 are provided in the power transmission path for the actuating force, the end of the power transmission path facing away from the workpiece is provided with an actuating member 14;
This actuating member distorts the elastically deformable links 8, 9, 11 at the start of grinding or polishing and connects this strained state until the desired value of the actuating force or pressure is obtained, and then during the course of the process The device is immobilized and includes means 10 for detecting the elastic deformation of the transmission link and its deformation changes occurring during the course of the process and for measuring both the actuating force or pressure and the wear depth from the values determined by the detection. An apparatus further comprising: (2) further comprising means for averaging the results of the measurements over one or multiple revolutions of the sample holder, the workpiece 2 being rotated during grinding or polishing of the sample holder 4, 15; An apparatus according to claim (1), which is guided by: (3) The means for measuring the actuation force or pressure and the wear depth consist of a microprocessor 25 encoded with parameters for controlling the process according to a desired program. 1
) or (2).